Liquid crystalline polymers (LCPs) are commercially sold for a variety of uses, and in many cases they have (combinations of) properties that can't be matched by other polymers. Many LCPs have good high temperature properties that are useful, for example from about 250° C. to about 320° C. There are other LCPs that have been claimed to be useful at higher temperatures, but these have often had other drawbacks, such as poor processability and/or poor thermal stability at their melt processing and/or use temperatures. There fore LCPs with improved high temperature properties are of interest. Described herein are such LCPs, which contain repeat units derived from 4,4′-biphenol, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid in a selected limited compositional range.
U.S. Pat. No. 4,849,499 describes copolymers containing the repeat units described above. None of the polymers actually made are reported to have melting points above 400° C., and the compositional ranges described herein are not mentioned.
Japanese Patent 7-47624B2 describes polymers with the repeat units derived from 4,4′-biphenol, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid. Although the compositional range described in this patent overlaps with the compositional range of this invention, no examples within the range of this invention are reported, and all polymers actually made have a “flow initiation temperature” below 320° C., and are reported to be liquids at 320° C.
Working Example 1 of Japanese Patent Application 8-41187 reports the preparation of an LCP derived from 4,4′-biphenol, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid and having a melting point of 387° C. The compositional range of this LCP is outside the compositional range claimed herein.